After the UK terror threat level was raised to critical – the highest level – the armed forces provided guards for places of interest and transport hubs in the capital, as part of Operation Temperer.

Assistant Commissioner Mark Rowley, head of national Counter Terrorism Policing, said: ‘We are grateful to the military who have neabled us to put even more police on the streets to protect the public at this time.’

Scotland Yard added that Operation Temperer was seeing the forces ‘do everything they can to protect the public’.

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This comes in the wake of a horrific terror attack at an Ariana Grande concert in Manchester, which killed 22 people.

Here's what we know about the Manchester attack so far:

The attack was carried out by 22-year-old Salman Abedi.

Abedi was a lone male suicide bomber who detonated an improvised explosive device.

22 people have been killed and 59 were taken to hospital following the blast. 119 people were injured in total.

Children are among the dead

The youngest named victim was eight years old

The lone attacker died at the arena

Police are investigating whether he acted alone or was part of a network

It is the worst terrorist attack in the UK since 56 people were killed in the 7/7 London bombings in 2005.

The explosion rocked the Manchester Arena at the conclusion of a performance by the American star Ariana Grande.

Manchester Arena said the explosion happened outside the venue, as people began streaming from the doors.

Greater Manchester Police said they were called to the venue at around 10.33pm and approach roads were closed.

The blast is being treated as a terrorist incident.

More than 400 officers were deployed on the operation throughout Monday night.

Manchester Victoria station was evacuated and trains cancelled.

The victims are being treated at eight hospitals across Greater Manchester, Chief Constable Ian Hopkins said.

The Prime Minister condemned what was being treated as an 'appalling terrorist attack' and said she would chair a meeting of the Government's emergency Cobra committee on Tuesday.

All national General Election campaigning was suspended after the explosion.

A controlled explosion was carried out by police at the Cathedral Gardens area near Manchester Arena shortly after 1.30am.

Police said the suspicious item at the centre of the controlled explosion was just abandoned clothing.

The first victim of the Manchester terror attack has been named as Georgina Callendar

Two more victims have since been named - 26-year-old John Atkinson, and eight-year-old Saffie Rose Roussos.

Police have arrested a man, 23, in connection with the terror attack at Manchester Arena.

Vigils were held in cities all over the country the next day, May 23

Theresa May has raised the UK's terror threat level from 'severe' to 'critical' - the highest level.

Theresa May has made a statement in Downing Street following the Manchester attack. She said: 'Our thoughts and prayers are with the victims and the families and friends of all those affected.

'It is now beyond doubt that the people of Manchester and of this country have fallen victim to a callous terrorist attack, an attack that targeted some of the youngest people in our society with cold calculation.

'This was among the worst terrorist incidents we have ever experienced in the United Kingdom.'